Aircraft are vulnerable to attack, particularly during takeoff and landing. In particular, aircraft flying at low altitudes during takeoff and landing are vulnerable to terrorist attack by shoulder-launched missiles, such as MAN Portable Air Defense Systems, or “MANPADs”. In recent times, such MANPADs have become widespread throughout the world because they are relatively inexpensive and easy to launch by unskilled personnel.
Conventional MANPAD-launched missiles include an infrared sensor that is sensitive to heat, for example the heat emitted from an aircraft engine. The missile is programmed to home in on the infrared heat signal using a steering system. Using a rotating reticle as a shutter for the sensor, the incoming heat signal is modulated, and, using the modulated signal, an on-board processor performs the calculations necessary to steer the missile to its target. Owing to its portable size, MANPAD missiles have a limited range, and a burn time of a few seconds from launch to extinguishing.
In recent years, missile guidance systems have become increasingly sophisticated, and, as a result, there are a number of different types of missiles in existence. In some embodiments, the missile is outfitted with multiple sensors that detect infrared radiation at multiple wavelengths, using reticles that are encoded at different patterns. More recently, missiles that employ a focal plane array (FPA) have been developed. Such FPA-based systems attack aircraft based on image processing, rather than heat or radar signatures, and are trained to attack vulnerable locations of the aircraft, i.e. cockpit and rudder, which are more susceptible to fatal attack than the engines.
In view of the threat, various countermeasure techniques have become popular. A missile warning system scans the region for rocket launch signals, such as the infrared or ultraviolet signature of a rocket tail. Upon the detection of a missile launch, various countermeasure systems are activated. In one example, hot flares or chaff are released from the aircraft to confuse the infrared or radar system of the launched missile. Other approaches broadcast light energy in order to confuse the missile infrared sensors. In one example, light energy emitted by non-coherent flashlamps is directed toward the missile sensors, in order to confuse them and render them ineffective (“jamming”). In Closed-Loop InfraRed CounterMeasure (CLIRCM) systems, the optical subsystem of the missile sensor is remotely interrogated to determine its optical modulation frequency. Coherent laser energy that is specifically encoded in a suitable format by the countermeasure system is then directed toward the missile sensors, thereby confusing, or jamming, the missile sensors, causing the missile to be steered off course. High-power laser energy can also be used to counterattack FPA-based systems, by disabling the focal plane array.
Owing to their extremely high cost, such countermeasure systems have enjoyed only limited use, primarily on military aircraft. The countermeasure systems are commonly integrated into the aircraft, for example, in the fuselage, wing, or nose of the aircraft, or fixed onto an outer portion of the aircraft. Depending on where the countermeasure systems are mounted to the aircraft, they can lead to an increase in drag, reducing flight performance and increasing operating costs. Also, servicing, maintenance, upgrading and testing of the systems are expensive and time consuming procedures. In addition, such procedures require grounding of each aircraft for a period of time.